This is a proposal for a K08 Mentored Clinical Scientist Research Career Development Award training program. The candidate, Dr. Richelle C. Charles, recently completed an Infectious Disease clinical fellowship in the combined training program between Massachusetts General Hospital and the Brigham and Women's Hospital, Boston. She is now in a period of extended research training in the Division of Infectious Diseases at the Massachusetts General Hospital, and plans to pursue a career as an independent biomedical investigator focused on mucosal and enteric infections of import in resource-limited areas of the world. This application proposes a five-year K08 training program under the primary mentorship of Dr. Edward T. Ryan in the Division of Infectious Disease of the Massachusetts General Hospital. Dr. Stephen B. Calderwood, within the same division, will provide co-mentorship throughout the course of the proposed program. The program involves both didactic and practical training focused on high-throughput immuno-proteomic approaches, and builds upon ongoing collaborations with the International Center for Diarrheal Disease Research, Bangladesh (ICDDR,B), Harvard Institute of Proteomics, and Arizona State University. The major project focus will be the application of immuno-proteomics to the study of protective immunity in human cholera infection, an infection that remains endemic in over 50 countries. An estimated 3-5 million individuals develop cholera each year, resulting in approximately 100,000 deaths. Although cholera vaccines do induce a protective immune response, immunity is short-lived, lasting approximately 6-24 months. In comparison, natural infection with cholera results in protective immunity that lasts years or decades; however, the mediators of the protective immune response to cholera are poorly understood. In this application, the trainee will use a high-throughput protein-based platform, the Nucleic Acid Programmable Protein Array, to (1) characterize serum anti-V. cholerae immune responses in cholera patients and vaccinees, and correlate baseline serum humoral anti-V. cholerae immunity with protection from disease in household contacts of cholera patients; (2) characterize mucosal anti-V. cholerae immune response, using the antibody-in lymphocyte (ALS ) assay, a marker of mucosal immunity, and (3) characterize anti-V. cholerae memory B cell responses during human wild-type V. cholerae infection, and correlate anti-V. cholerae memory B cell immunity with protection from disease in household contacts of cholera patients. Antigens identified by high throughput screening will then be examined in more detail, including in immunologic confirmatory studies. The results of these studies could provide important insights into protective immunity of human cholera infection, and could lead to improved vaccination strategies against cholera. A K08 award would provide the candidate with critical skills and experience in scientific investigation, and facilitate her development into an independent physician scientist.